1. Field of the Invention
The invention relates in general to the joining of aluminum conductors, and more specifically to MIG arc spot welding of aluminum conductors to form electrical conductor connections.
2. Description of the Prior Art
Aluminum has successfully replaced copper in a large number of electrical conductor applications. Whether or not aluminum may be successfully used in a specific conductor application is usually dependent upon the availability of an economical and reliable process for making joints between conductor members.
Copper can be readily soldered with rosin-type fluxes with no corrosion problems due to flux residues, and copper can be fluxless brazed in air using certain brazing alloys. Aluminum soldering generally requires the use of fluxes which leave corrosive residues, and these residues thus must be completely removed to avoid corrosion problems. Aluminum can be successfully brazed in a vacuum, but vacuum-brazing is limited to those applications susceptible to the placement of the entire assembly in a vacuum chamber.
Aluminum conductors can be welded, with a common aluminum welding process being gas-shielded metal arc spot welding using consummable electrodes, hereinafter referred to as MIG arc spot welding.
Certain of the coils in distribution-type transformers are formed of aluminum strip. Copper, however, has been used to form the conductor members which make the internal connections to the aluminum strip, as well as for making the flexible leads which proceed from the internal connections to the bushing studs. Substantial cost savings are possible by replacing these copper connections and leads with aluminum members, but an appropriate joining technique for making aluminum-to-aluminum joints must be developed before the savings can be realized. The joining technique must be applicable to production line techniques, it must be reliable and reproducible with minimum operator skill level, it must be low cost, and it must produce joints which may be visually inspected for joint integrity.